After suffering limb loss, upper extremity amputees generally have two options in prosthesis types for functional replacement of the hand - body powered or myoelectric type devices - both of which offer very limited restoration of hand function. Recent advances in robotics technology have enabled multigrasp hand prostheses which hold the promise of greatly enhancing functional replacement of the missing hand. Such prostheses, however, will not be useful without a user interface that enables the amputee to quickly, easily, and effectively assess the multigrasp capability of the hand. The investigators have developed a user interface for a multi- grasp prosthesis that (based on preliminary work) provides intuitive, real-time, direct control of multiple hand postures. The proposed control structure augments EMG information from the user with position and force in- formation from sensors in the hand, and leverages this combined information to provide a degree of semi- autonomous coordination, which in turn greatly simplifies the user's control of and interaction with the hand prosthesis. As such, the objective of the proposed work is to implement this multigrasp myoelectric control interface on a multigrasp hand prosthesis on five unilateral transradial amputee subjects, and assess the efficacy of the multigrasp hand when performing manual tasks, relative to their state-of-the-art single-grasp myoelectric prosthetic hands. The outcome of the efficacy study could either validate, or bring into question, the functional merit of multigrasp hand prostheses relative to the single-grasp state-of-the-art. PUBLIC HEALTH RELEVANCE: As of 2005, there were approximately 41,000 persons living in the United States with major (i.e., excluding loss of fingers) upper limb amputations. Current hand prostheses offer these amputees very limited restoration of hand function. This study proposes a prosthetic hand and interface controller that could provide considerably improved restoration of hand function, and thus could offer considerably improved quality of life for upper extremity amputees.